Cavity drill



C. E. HELLMA N July 7, 1925.

CAVITY DRILL 1 Filed May 26. 1925 3mm 0.11. Hellman.

Patented July 7, 1925.

UNITED STATES CHARLES E. HELLMAN, OF EAGLE PASS, TEXAS.

CAVITY DRILL- Application filed May 26,

To all whom it may concern:

Be it known that I, CHARLES E. HELLMAN, a citizen of Finland, residingat Eagle Pass, in the county of Maverick and State of Texas, haveinvented certain new and useful Improvements in Cavity Drills; "and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

The invention has for its object the provision of a drill bit for miningand tunneling operations, whereby the opening may be enlarged at thebottom to permit a greater area for the placing of an explosive where itwill do the best work and develop a greater force by a less amount ofexplosive than by the old method.

A further purpose of the invention is the provision of a drill bit forfinishing the opening which is enlarged, thereby making it possible toconcentrate the explosive at the bottom of the opening and therebyrendering the same more effective.

' Other objects and advantages will be apparent and suggest themselvesas the nature of the invention is understood.

lVhile the drawings illustrate anembodiment of the invention it is to beunderstood that in adapting the same to meet different conditions andrequirements, various changes in the form, proportion and minor. detailsof construction may be resorted to without departing from the nature ofthe invention.

Referring to the accompanying drawings forming a part of theapplication: 7

Figure 1 is a front edge view of a drill bit embodying the invention,

Figure 2 is aside view of the bit looking at it from the left side ofFigure 1, and

Figure 3 an end view thereof.

Corresponding and like parts are referred to in the followingdescription and designated in the several views of the drawings by likereference characters.

The numeral 1 designates the drill bit which is made of the samematerial as other bits and is designed to be used as a finish bit forenlarging the lower end of the open- 1923. Serial No. 641,638.

ing. The bit consists of a fiat bar and its active or cutting end isextended laterally at one side only, as indicated at 2. The opposite orrear edge 3 of the bit is straight. The lower end of the bit is inclinedthroughout its length, as indicatedat 4;, and is beveled from oppositesides to a cutting edge. The lateral extension 2 is likewise beveledfrom opposite sides to ,a cutting edge, as indicated most clearly inFigure 3. Thepassageway 5 extending through the bit isdeflected'laterally at the lower end, as

indicated most clearly in Figure 1. This passageway is adapted for theforcing of water through itto expunge mud or cuttings and also tominimize heating of the bit. The lower cutting edge 4: inclinesforwardly and downwardly from the rear edge 3 and intersects with theforward cutting edge of the lateral extensionQ. The rear edge 3 istransversely curved, as indicated most clearly in Figure 8. The bit isoperated in the well known manner, being reciprocated and rotated and ateach downward movement of the bit, the inclined edge 4 glancing on thebottom of the opening results in a lateral movement of the bit wherebythe cutting edge of the lateral extension 2 operates laterally on theside wall of the opening, thereby enlarging the same with the resultthat the bottom of the opening is enlarged to receive the explosivewhich is confined by the portion overhanging the enlargement with theresult that the explosion of the charge results in greater executionthan ordinarily.

What is claimed is:

1. A bit having a lateral extension at its lower end and having thelatter inclined forwardly and downwardly from the rear edge of the bitand intersecting with the forward cutting edge of the lateral extension,both the lower end of the bit'and the outer edge of the lateralextension being beveled from opposite sidesand throughout their lengthto form cutting edges;

2. A bit of the character specified having its rear edge straight andtransversely curved, and having a lateral extension at its lower end andhaving the latter inclined forwardly and downwardly from the rear edgeand intersecting the outer edge of the lateral extension, both the lowerend of the bit and the outer edge Ofthe lateral extension being beveledfrom opposite sides and throughout their length to form cutting edges,and said bit having a water passage therein which is deflected at theoutlet laterally to one side of the lower cutting edge. In testimonywhereof I aflix my signature in presence of two witnesses.

CHARLES E, HELLMAN. Witnesses:

H. P. MATHIS, A. B. BOUBEL.

